Concord with quantifiers

1 A large number of guest workers .... offered subsidized passages to Australia every year. is are 2 An increasing number of migrants .... to their countries of origin. returns return 3 A pair of slacks (= lange broek, sportpantalon).... more expensive than you think. is are 4 Lots of coal .... lying on the road. was were 5 A lot of people ..... that Stonehenge was a Druid temple. believes believe 6 Plenty of little white sheep ...... grazing in the valleys. was were 7 There ... lots of fruit on the table. was were 8 Because of inflation lots of private property ........ offered for sale. is are 9 A number of carefully selected volunteers ......... in hospitals and mental homes. works work 10 There ..... a lot of salmon in the rivers. was were 11 A large number of people ...... applied for the job. has have 12 Lots of practice ........ very useful. is are 13 There .... plenty of parking space behind the theatre. is are 14 A lot of difficulty ..... caused by mother tongue interference. is are 15 There ... lots of racial trouble in some larger English towns. is are